it is a tricky situation, because when both parents are denying that something is wrong, it will just get worse no matter hjow much you help. your mum should have the courage to say to your dad that she doesnt love him anymore and that she wants to move on. but then, if she does love him, things need to change between them. and all this depends on how he feels, if he still loves her he needs to admit that a change is required, but if he doesnt he should move on.

i wish you and your family all the best. take care

simon